Fabrication Process of CdS-Cu S Cells

The back contact on the substrate is produced by evaporating a thin Cr film which acts as an adhesive interlayer and a 1 ym thick Ag film. The geometrical arrangements of the back contact areas have been designed according to the interconnections between the cells in the integrated panel and to the technical requirements (output voltage, output current). 

The evaporation system for deposition of a 30 ym CdS film is shown in figure 27. The size of the crucible is 15 x 30 cm. The temperature of the crucible during deposition is lOOO the substrate temperature is 200 C. The evaporation system can be used both for cell and module production. 

After evaporation the CdS film is etched in HC1 H20 solution at a temperature of 60 C for about 10 seconds. This etching process results in a surface roughness and a pyramidal structure of 1-3 ym size as demonstrated in figure 7. In the next step of fabricatioij the Cu S layer is grown topotaxial by dipping in an acid solution of CuCl at 90 °C. Finally an additional 50 8 Cu film is deposited on the heterojunction system. After heat treatment in air at temperature of 200 °C the system shows optimum photovoltaic efficiency. 

Contacting and encapsulating take place in a press. The principle of operation, schematically sketched in figure 28, includes evacuation, pressing and heating the hot setting adhesive 

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